追記

gdb によるメモリダンプについて

(gdb) help dump binary memory
Write contents of memory to a raw binary file.
Arguments are FILE START STOP. Writes the contents of memory
within the range [START .. STOP) to the specifed FILE in binary format.

core から文字列等を検索する

リークしている領域の特徴に当たりがついていれば gdb の find で見つけるという方法もある。

(gdb) help find
Search memory for a sequence of bytes.
Usage:
find [/size-char] [/max-count] start-address, end-address, expr1 [, expr2 ...]
find [/size-char] [/max-count] start-address, +length, expr1 [, expr2 ...]
size-char is one of b,h,w,g for 8,16,32,64 bit values respectively,
and if not specified the size is taken from the type of the expression
in the current language.
Note that this means for example that in the case of C-like languages
a search for an untyped 0x42 will search for "(int) 0x42"
which is typically four bytes.
The address of the last match is stored as the value of "$_".
Convenience variable "$numfound" is set to the number of matches.